As I put it in this piece, the year of the car as a service has finally arrived. One small hiccup for Zipcar: It’s not profitable, and likely won’t be profitable this year. For the year ended December 31, 2010, Zipcar generated revenue of $186.10 million, with a net loss of $14.12 million. As of December 31, 2010, Zipcar had an accumulated deficit of $65.4 million, and in the company’s risk factors in its S1, it says, “We expect to incur a net loss in 2011. We do not know if our business operations will become profitable or if we will continue to incur net losses in 2012 and beyond.”

Car sharing is an expensive business when you have to own and maintain the cars in the fleet. As of September 2010 (when I did this analysis), Zipcar had 8,541 cars in its fleet, most of which it leased, but 1,692 of which it owned outright. Most of Zipcar’s costs are maintaining cars, and buying and selling the cars, which it only keeps on an average of two to three years before it sells them to the used-car market.

A less capital-intensive version of car sharing is neighbor-to-neighbor car sharing, which is being promoted by startups like RelayRides and Spride Share. (Hear from these companies at Green:Net 2011, on April 21 in San Francisco.) In this next-gen car sharing world, the members of the community own the cars and rent them out to their neighbors.

Zipcar needs the $174.24 million to expand its fleet and bring in more users; there are only 560,000 members after eleven years in business. But, according to Frost & Sullivan, the revenue from car sharing programs in North America will increase to $3.3 billion in 2016, up from $253 million in 2009.